Note: Descriptions are shown in the official language in which they were submitted.
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Gerking, Liider
(N15)
Spinning device for producing fine threads by splitting
The invention relates to a spinning device for producing
fine threads by splitting according to the preamble of the
main claim.
Fine threads into the range below 1 micrometre (pm) can be
produced by splitting a thread-forming fluid flow as a
melt, solution or in general as liquids which are
subsequently made to solidify, as has been described in DE
199 29 709 and DE 100 65 859. The mechanism of thread
formation is fundamentally different from all the spinning
methods which have become known to date where the spinning
material is withdrawn by winding-up devices from the
spinning nozzles to form threads or, in the case of
spunbond methods, by accompanying airflows which exert a
force on them and, in a special embodiment, in the so-
called meltblown methods, where the air drawing the thread
emerges right beside the spinning nozzle openings heated to
approx. spinning material temperature. The thread speed
thereby achieves that of the winding or is below that of
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the air- or gas flows drawing it. This applies to the
average of thread diameters, however individual "mavericks"
are discovered during the meltblown method where also finer
diameters can arise than that from throughput and maximum
possible withdrawal speed, the greatest air speed, but
still not in a targeted manner as happens in the mentioned
new method, also termed Nanoval method. Here the following
effect is used according to a new mechanism, only explained
recently from hydrodynamic basic rules, see L. Gerking in
Chemical Fibers International 54 (2004) pp. 261-262 and 56
(2006), pp. 57-59: if a melt- or in general fluid thread or
-film is impinged upon by shear stresses externally, then
the result in the interior thereof is a pressure build-up
if the speed on the outer skin of the fluid jet is greater
than that in the interior thereof and this is even more the
case the greater is the acceleration thereof that can be
achieved after emergence from the spinning opening. This
is, one can say, the reverse of flow in pipes or channels
(Hagen-Poiseuille) where the pressure energy is used to
overcome the friction on the channel walls whilst, in the
case of the new spinning method, energy is transmitted to
the thread by the shear stresses acting thereon from the
exterior. Said thread attempts to counteract this by a
pressure increase in the interior. If not only the outer
skin is cooled by the gas flow surrounding it then the
result can be solidification of the thread.
In the case of polymers and polymer solutions with their
basically low heat conductivity, firstly however only an
outer skin of increasing viscosity is formed and the
hydrodynamic effects can act in the interior of the thread.
The result then is, with good regularity and
reproducibility, a bursting which is comparable with the
bursting of pipe on its longitudinal join with
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astonishingly essentially continuous threads and, in view
of the stochastic character of the splitting, of a low
distribution width in the thread diameter. The number of
individual threads produced in this way exceeds, in the
production of particularly fine threads, in the range
around and below 1 um, up to several hundreds from one
liquid jet.
The Nanoval method is carried out in lines of nozzles in
its industrial applications, a series of spinning orifices
being located above a gap. The gas, in general air,
without particular conditioning after its production in
fans or compressors (the energy requirement is
fundamentally low compared with the meltblown methods)
flows at both sides of the line of nozzles in constant
acceleration towards the narrowest cross-section of the gap
which then again generally rapidly widens, basically
however has the configuration of a Laval nozzle. Also
individual round nozzles were described surrounded by an
annular gap which constantly reduces towards the narrowest
cross-section.
It has been shown that the shear forces acting on the
thread on all sides by a rotationally symmetrical gas flow
lead to a smaller average diameter of the essentially
continuous threads which are produced by splitting, which
can be attributed to the more uniform impingement of the
thread, irrespective of whether the air is also heated
additionally or not. Also the cooling which, in interplay,
causes the bursting effect with the hydrodynamic forces is
distributed more uniformly around the thread than happens
in the case of merely lateral impingement in the lines of
nozzles with a linear Laval nozzle configuration and less
air is consumed. In the case of the lines of nozzles, a
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part of the air is used more poorly in the intermediate
spaces from thread to thread.
A further influential factor for the production of fine and
ever finer threads, as can be produced otherwise for
example only by electrospinning methods, however in very
small throughputs and with a high spatial and safety
expenditure because of the required high voltage, is the
throughput per spinning nozzle opening, irrespective of
whether with round or slot-shaped openings for the spinning
material. The gas speed in the narrowest cross-section of
the Laval nozzle can achieve the speed of sound, thereafter
in the widened section even into ultrasound, which then, in
the case of this flow laden with threads, generally leads
rapidly to subsonic sound by means of compression shocks.
However, only a specific shape changing operation can be
performed by the shear stress forces in the case of a given
running surface of the still deformable thread material.
The throughputs are consequently fundamentally lower when
producing very fine threads in the range around and below 1
um. This leads to the fact that, for a specific total
throughput when producing nonwovens according to the
Nanoval method for finer threads, more spinning nozzles are
used over the width. This applies correspondingly in the
production of yarns.
The object underlying the invention is to produce a device
for producing fine threads which is compact and
constructionally simple, a good start to spinning being
intended to be possible.
This object is achieved according to the invention by the
characterising features of the main claim in conjunction
with the features of the preamble.
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As a result of the features represented in the sub-claims,
advantageous developments and improvements are possible.
As a result of the fact that the device for producing fine
threads has at least one spinning nozzle part which is
equipped with spinning nozzles and at least one partially
plate-shaped gas nozzle part with at least one gas supply
chamber, the at least partially plate-shaped gas nozzle
part having a plurality of funnel-shaped depressions as
acceleration nozzles into which the spinning nozzles engage
in such a manner that combinations of spinning
nozzles/acceleration nozzles, in particular Laval nozzles,
with rotationally symmetrical gas flow channels are formed,
the device can be constructed compactly with a large number
of closely adjacent combinations, gas nozzle part and
spinning nozzle part being displaceable relative to each
other so that the gas flow channels which are formed
between gas nozzle part and spinning nozzles of the
spinning nozzle part can have different flow cross-
sections, as a result of which the height of the spinning
openings can be adjusted to the narrowest cross-section of
the acceleration nozzles, in particular Laval nozzles. As
a result, the start of spinning is facilitated and made
possible for the first time ever with a plurality of
nozzles which are adjacent and in succession in that the
gas nozzle part is withdrawn relative to the spinning
nozzle part towards the latter in order not to impair the
arriving thread run. At the same time, maintenance and
cleaning of the spinning nozzles is facilitated as a result
of the displaceability.
A particularly simple construction is provided if the gas
chamber is formed between the underside of the spinning
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nozzle part, out of which the spinning nozzles or spinning
nipples protrude, and the upper side of the plate-shaped
region of the gas nozzle part, the gas, usually air, being
supplied to the acceleration nozzles via said gas chamber.
It is particularly advantageous to provide a self-adjusting
seal between the spinning nozzle part and gas nozzle part,
which is compressed when introducing the gas during
spinning by the then resulting pressure.
An advantageous embodiment, although somewhat more complex
and in particular when supplying "cold" air, resides in
configuring the gas nozzle part as a hollow body which is
engaged by the depressions and the cavity of which between
the depressions forms the gas chamber, the hollow body
having openings which are directed towards the spinning
nozzle part, preferably rotationally symmetrically about
the depressions, via which the air or the gas passes
towards the acceleration nozzles.
A plurality of nozzle parts and gas nozzle parts can be
disposed adjacently, different spinning materials also
being able to be spun.
Advantageously, a further plate with openings can be
disposed below the plate-shaped region of the gas nozzle
part, forming a distributor chamber for a further fluid.
This fluid can be water for coagulating dissolved fibre
materials, coolant for freezing the molecular orientation
achieved during the splitting, means for heating, e.g.
steam, for a second stretching or the like.
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The invention is represented in the drawing and is
explained in more detail in the subsequent description.
There are shown:
Fig. 1 a longitudinal section through a first embodiment
of the spinning device according to the invention
corresponding to the section lines D - D
according to Fig. 2,
Fig. 2 a section of the device according to the
invention according to the section lines C - C of
Fig. 1,
Fig. 3 a section through a part of the device according
to the invention according to a second embodiment
corresponding to the section line A - A in Fig.
4, and
Fig. 4 a section through the device corresponding to the
section line B - B in Fig. 3.
The spinning device represented in Fig. 1 and 2 has a
spinning nozzle part 28 in which a plurality of melt
channels 14 is provided, said melt channels being provided
via a filter 25 and a perforated plate 26 for cleaning
supplied melt or solution with melt or solution. The melt
channels continue into spinning nozzles or spinning nipples
23, only three rows of spinning nipples 23 being shown
here. A plurality of spinning nipples can perfectly well
be provided in succession in the direction of travel
according to arrow 50.
The lower plate-shaped region of the spinning nozzle part
is received in a gas nozzle part 27 which comprises a
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frame-like edging 34 and a plate-like part 35, in the
latter three respectively offset rows of Laval nozzles 36
being provided corresponding to the rows of spinning
nipples 23. The edging 34 is provided with an upright
edge, a seal 33 being disposed between this upright edge
and a surface 32, which is situated opposite said upright
edge, of the lower region of the spinning nozzle part 28.
The spinning- and the gas nozzle part 28, 27 are aligned
relative to each other such that the tip of the spinning
nipples 23 protrudes into the Laval nozzles 36, a gas
chamber 22 being formed between the lower surface of the
spinning nozzle part 28 and the upper surface of the plate-
shaped region 35 of the gas nozzle part, through which gas
chamber the spinning nipples 23 engage and which is
connected to gas or air supply lines 20 provided in the
edging.
In particular if the supplied air is cold, the spinning
nipples 23 are preferably provided with a heating means 24,
advantageously with a belt heating means, as is known from
injection moulding tools in plastic material machine
construction.
The device according to the invention has means for
displacement of the spinning- and gas nozzle part 28, 27
relative to each other, a screw 29 being guided, in the
present embodiment, in a split nut 30 which is securely
connected to the spinning nozzle part and is connected in
an anchor 31 in the frame 34 of the gas nozzle part 27 to
the latter, the anchor 31 being able to exert a pressure or
tension force according to the direction of rotation of the
screw 29, as a result of which the gas nozzle part is
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displaced. Of course, other types of displacement means
are possible.
For the start of spinning, the gas nozzle part 27 is
raised, i.e. displaced upwards in Fig. 1, as result of
which the seal 33 is relieved of pressure. If, after
arrival, the gas 21 is supplied via the supply line 20, a
pressure force on the seal 33 is increased by the pressure
in the gas chamber 22 in addition to a displacement of the
gas nozzle part 27 downwards. Hence a specific self-
adjustment of the seal is produced upon arrival of the melt
or solution and release of the Laval nozzle cross-section
towards the individual spinning nipples.
In order to clean the spinning nipples 23, the gas supply
21 is switched off, the gas nozzle part 27 is raised until
the plate part 35 abuts against the spinning nipples 23
with the wall of the Laval nozzles 35. The air present in
the region of the seal 33 and the surface 32 is thereby
blown out. The nipples 23 protrude out of the Laval
nozzles and can be cleaned.
The device represented in Fig. 3 has a spinning nozzle part
1 with a series of raised portions or projections,
preferably in conical form, which receive or form the
spinning nozzles 13. For example, the spinning nozzle part
can be configured as a plate into which the spinning
nozzles 13 (similarly to Fig. 1) are inserted. The
spinning nozzles have melt or solution channels 14 which
end in a spinning nozzle opening 3.
Furthermore, a gas nozzle part 2 is provided which is
configured for example as a hollow body which is formed by
two plates provided with funnel-shaped depressions.
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Between the plates, a cavity 9 is formed which is
interrupted by the funnel-shaped depressions. The cavity 9
serves as gas chamber which is in turn connected to a gas
supply source. Around each funnel-shaped depression, an
annular opening 4 is incorporated, the openings 4
represented in section in Fig. 3 being intended
corresponding to Fig. 4 in common for adjacent funnel-
shaped depressions, i.e. in the embodiment, the funnel-
shaped depressions are disposed closely adjacently.
The conical raised portions which form the spinning nozzles
13 engage in the depressions of the gas nozzle part 2 such
that rotationally symmetrical gas flow channels 5 are
produced. In the represented embodiment, respectively in
the intermediate space between the spinning nozzles 13
which are represented in Fig. 3 as depressions, yet another
insulating formed part 11 is introduced which forms an air
gap 12 and extends up to the spinning opening 3 so that the
gas flow channel 5 between the surface of the formed part
11 and surface of the depression in part 2 is formed around
the space 9. The respective gas flow channel 5 is thereby
configured such that it tapers in the direction of the
respective spinning opening 3 around which the respective
depression engages rotationally symmetrically. Hence
respectively a Laval nozzle is produced, the cross-section
of which widens abruptly at the edge between depression and
outer surface of the lower plate in Fig. 3, which however
can also take place gradually.
The spinning nozzle part 1 and the gas nozzle part 2 are
displaceable relative to each other, viewed according to
Fig. 3, in the perpendicular direction, which can be
achieved by sliding rods, not shown. Consequently, the
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height of the narrowest position 6 of the Laval nozzle can
be adjusted relative to the spinning opening 3, as a result
of which the start of spinning can also be facilitated.
These sliding rods can absorb force produced at the same
time with different expansions of the spinning nozzle- 1
and of the gas nozzle part 2, as a result of which the
positioning of both parts relative to each other is
maintained.
In Fig. 4, two rows of combinations of spinning nozzles 13
and Laval nozzles, ending at the narrowest cross-section 6
are represented, the spinning nozzles 13 of one row being
offset relative to those of the other rows. It is possible
in particular with greater spinning beam widths that
special gas distribution channels are also provided between
adjacent rows in order to supply the required gas
quantities to the Laval nozzles.
The mode of operation is dealt with in the following.
In Fig. 3, the melt is supplied in part 1 and emerges in
the spinning nozzle openings 3, whilst the gas,
subsequently termed air, flows out of the space 9 in part 2
after emergence via the annular opening 4 towards the
channel 5, which is rotationally symmetrical relative to
the spinning nozzle opening 3, between part 1 and 2 towards
the narrowest cross-section 6 and in advance grips the
emerging thread 7 at the spinning opening 3, accelerates
it, i.e. reduces it in diameter and, according to the
Nanoval effect, causes it already in the Laval nozzle or
shortly thereafter to burst into a thread bundle 8 like a
brush.
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Whilst the start of spinning with a line of nozzles takes
place simply by pushing together two channel halves which
form the Laval nozzles, this is not possible in the case of
nozzle combinations in a plurality of rows. The part 2 can
however be displaced in the direction of the thread
emergence axis. As a result, it can be entirely drawn back
when starting spinning towards the formed part 11, an
expulsion of spinning air via the openings 4 can initially
be stopped or permitted to a small extent. Then the part 2
is lowered, spinning of the thread is started, it is drawn
and made to burst according to the setting data known from
the method for the air speed from the applied pressure in
the space 9 of part 2, for the flowing spinning material
from the openings 3 and at the temperature of the spinning
material required for splitting. Said material is
advantageously heated in addition just before emergence
from the spinning openings 3, indicated by heating means
10, the introduction and mounting of which has been
dispensed with for the sake of clarity of the drawing. In
order that the flowing air does not cool impermissibly at
lower temperatures than the spinning material temperature,
the formed part 11 is configured such that it, on the one
hand, forms the inner wall of the rotationally symmetrical
channel 5 for constant acceleration of the air until close
to the spinning nozzle opening 3 but, via an air gap 12,
also insulates the spinning nozzle 13 with respect to heat
against the airflow in the flow channel 5. The formed part
11 can however also contain heating means of the spinning
nozzles instead of the spinning nozzle part 1.
The two basic positions of the movable part 2 are indicated
in Fig. 3, in dotted lines for the start of the spinning
process.
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Fig. 4 shows a horizontal section B - B (in Fig. 3) as
section through a multirow nozzle device for two rows of
nozzles in order to illustrate the air supply from the
exterior to the individual spinning nozzles 13 for supply
from the space 9 via the openings 4 into the channels 5
which end respectively at the smallest cross-section 6.
In the case of a greater air requirement, i.e. in the case
of larger nonwoven and hence spinning beam widths, main
distributor channels can be fitted between the nozzle
openings, only the rows of individual nozzles moving apart
slightly in the nonwoven running direction because the
spinning nozzle device according to the invention has the
advantage as spinning beam at the same time that it forms a
plurality of spinning beams in succession viewed in the
nonwoven running direction. Each has its specific
irregularities, even from hole to hole, as in the case
shown here with spinning nozzle and Laval nozzle beyond the
nonwoven width. A statistical compensation for greater
nonwoven uniformity can take place between the individual
rows because the threads of the following rows increasingly
cover the sparse positions of the preceding ones.
If in addition gas or air or a liquid medium for
accompaniment of solutions is desired for cooling or
keeping warm during spinning of said solutions also for
coagulation of the threads, then this medium can easily be
introduced as third fluid flow between the spinning and
Laval nozzles and be made to flow out. This is illustrated
in Fig. 1 by a plate 37 which is provided with openings 38
respectively below the spinning nipples 23 and the Laval
nozzle-like openings 36. Similarly as with the air supply
to the space 22, the third fluid flow, at 39 according to
arrow 40, can be introduced into the space 41 formed
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between the plates 35 and 37. It passes from there via the
upper edges of the openings 38 into the thread air flow.
This can take place for example by introducing the
coagulation of pulp from lyocell solution threads, as
described in DE 100 65 859 in more detail. The size of the
openings 38 and their position relative to the spinning
nipples 23 can be easily coordinated to the main flow of
the thread with the surrounding gas. All three fluids
thereby flow downwards (in the drawing).
The device is also fundamentally suitable for spinning
different spinning materials in the individual spinning
nozzles, for which purpose the melt- or spinning solution
distribution must be correspondingly arranged, i.e.
alternating transversely relative to the direction of
travel or also differently from row to row. It is hence
possible to produce mixed nonwovens in order to achieve
special effects, such as the spinning of binding threads in
matrix threads, e.g. polypropylene as binding threads and
polyester as the matrix which provides strength or by means
of a portion of more greatly shrinking threads in order,
after the nonwoven deposition, to achieve higher volumes
and softness as a result of shrinkage of the entire thread
web and also other nonwoven properties by means of two or
more different components. Also bicomponent or
multicomponent threads can be produced without difficulty
by supplying two or more spinning materials into the
spinning nozzle part and into the channels 14. With
different throughputs, adjusted by opening cross-sections
of the spinning nozzle openings of different sizes or by
controlled melt supply to the latter, a different type of
mixed nonwoven can be produced.
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The present device has in addition the advantage that it
connects the melt-guiding spinning nozzle parts 1 or 28 to
the colder gas nozzle parts 2 or 27, in fact in a mutually
displaceable manner but securely transversely relative
thereto. After heating part 1 with heating means, not
shown here, part 1 will expand more relative to 2 if no
particularly heated air is supplied from part 2 so that
respectively spinning boring 3 and narrowest cross-section
6 show deviations over the width and length, the same is
true for parts 28 and 27. The connection can take place by
means of sliding rods, not shown, which prevent this
deviation with respect to the forces, said sliding rods
being able to be disposed in the plates of the spinning
nozzle part 1 and of the gas nozzle part between the
combinations of spinning nozzle/Laval nozzle. In order to
prevent the different expansion, heating of the air flow in
the flow channel 5 can however also be undertaken
intentionally.
Guiding part 1, which is initially set back relative to the
spinning boring opening 3, and later is displaced in the
running direction of the thread 7 in order to produce the
splitting effect, must take place by means of guides or
sliding rods which are known in tool construction. The
introduction of air, likewise not shown here, takes place
from the exterior to the front, rear or side on the
spinning beam, a seal requiring to be present between
spinning nozzle part 1 and gas nozzle part 2 or because a
few millimetres of guidance length between 1 and 2 suffice,
the chambers 9 shown in Fig. 4 can also be fed via
corrugated bellows around the spinning beam and an outer
distribution chamber.
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It is now also possible in a simple manner to divide
spinning beam of a larger width into a plurality of nozzle
fields, these in turn comprising numerous individual
spinning nozzle/Laval nozzle combinations so that
individual ones of these packets (spinning packs) can be
exchanged in the case of blockages of the spinning openings
or other disruptions. The separating gaps are then
arranged diagonally relative to the running direction, the
spinning nozzle openings, as shown in Fig. 4, being
disposed respectively on the gap of the previous one.
The following example shows the use of the device in the
splitting spinning method according to Nanoval and the
thread values achieved for example. A polypropylene melt
was distributed to nineteen spinning nozzles 13, disposed
in a row, with inlet borings for the melt 14 and spinning
nozzle openings with a diameter of 0.3 mm. In the thread
running direction, there was situated thereafter for each
of these openings a Laval nozzle with the narrowest cross-
section of 3 mm diameter which was guided back to the
spinning opening after the start of spinning. The polymer
throughput was changed in regions as reproduced in Table 1,
likewise the air pressure and hence the flowing air speed
in the region of the shear stresses on the thread leading
to splitting. The temperature of the polypropylene melt
could be heated in the spinning nozzles 13 by approx. a
further 20 C shortly before emergence thereof from the
spinning opening via electrical heating elements.
For a device according to Figs. 1, 2, no substantially
different results are produced with the same method data.
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Melt Air Thread result
mo Ta Qpk Ta dso CV dv'i" dmez
g/min 0 C mbar a C pm t PM 1=
1,5 330 403 43 3,9 38 1,72 8,2
330 600 47 2,2 23 1,22 3,6
330 800 56 2,2 45 0,87 4.4
334 400 230 1,5 47 0,87 3,5
335 600 230 2.0 40 0,67 3,8
336 0,78
808 233 1,5 40 3,1
3,0 344 400 230 2,4 33 0,61 3,9
344 600 230 2,1 33 1,12 3,4
344 800 230 1,5 47 0,44 3,4
352 400 46 2,1 48 0,77 4,9
352 600 46 1,2 42 0,31 2,2
352 800 46 1,3 31 0,48 2,3
351 600 180 1,2 33 0,63 2,3
351 600 220 1,0 40 0,44 1,8
351 600 220 1,1 27 0,49 1,8
Table 1 Thread results polypropylene (PP)
MFI 28 Melt index at 230 C and 2.16 kg
mo polymer throughput per spinning boring
TS melt temperature
Apk air pressure before acceleration in the Laval nozzle
TL air temperature at the same place
d5o average thread diameter from 20 individual
measurements on the microscope screen
CV statistical scatter/d50 = 100 % variation coefficient
of the produced thread diameters
dmin smallest measured thread diameter respectively
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It is obvious that, not necessarily only at higher air
pressures, i.e. higher air speeds, higher air temperatures
and lower throughputs, the fine threads could be produced
down to approx. 0.5 pm = 500 nanometres (nm) but that this
was also achieved at greater throughputs of 3 g/min and
hole, for which purpose the temperature of the melt was
however increased before emergence thereof from 335 to
352 C, the air temperature remained initially, at the
higher throughput of 3.0 g/min, still in the range of that
produced by the compression and the increase at otherwise
constant values to 180 C produced no measurable influence
in the direction of higher fineness. Only an air
temperature increased to 220 C then produced the value ds0 =
1}un with minimum diameters of 0.44 measured in the
microscope. A thread measurement as here with the
microscope can however no longer claim high precision since
the range is already that of lightwave length. In any
case, unequivocal dependencies are there which initially
are surprising from the point of view of conventional
spinning. If it is recalled however that here threads are
produced by bursting, i.e. fragmentation, then rules other
than those of pure length drawing, are in operation as
described above, which lead to the fact that individual
parameters can be changed, such as for example the melt
temperature relative to the gas speed, with the same effect
on the resulting average thread diameter and even its
scatter.
Although the device according to the invention is intended
primarily for the production of fine threads, also coarser
ones can be spun with it, as a result of which the
versatility thereof is displayed. Thus, threads made of
polyester and polylactide were produced, as reproduced in
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Tables 2 and 3. The diameter of the spinning nozzle
openings was 1.0 mm.
mo TS Aytk TL dso Cv dtsn de"
g/mia OC Mbar C IIM !k 34M Jim
5,2 288 550 108 10,1 47 4,1 20,0
332 1000 271 4,2 43 1,5 9,9
10,0 299 500 270 15,3 23 7,4 19,8
271 1000 106 19,0 35 8,0 26,9
15,0 325 540 167 23,2 25 9,8 36,6
330 1000 165 11,3 65 4,2 33,2
Table 2 Thread results polyester (PET) i.v. = 0.64
intrinsic viscosity (textile type)
When spinning polyester threads, it proved to be of
advantage to withdraw the threads after they had burst
through an injector channel which was situated a good 1
metre lower, as described in L. Gerking, Change in Filament
Properties of Polymer and in the Spinning Line, Chemical
Fibres/Textile Industry 43/95 (1993) on pages 874/875. By
repeated heating in between, as described in DE 19 65 054
column 4, lines 44 to 57, the tensile strength of the
threads could be increased with both measures but primarily
the shrinkage was able to be significantly reduced.
The polymer polylactide produced from natural raw materials
showed in splitting spinning for coarser threads the values
reproduced in table 3.
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qb Ta liPk Tr dso CV dq,tn d.;.
glmin C mbar C IIm It 1s 1M
5,2 253 352 35 26,6 19 13r5 33,9
254 352 35 14,4 37 4,4 27,7
254 780 44 16,4 56 5,0 48,3
7,6 294 507 52 6,5 43 2,0 11,1
9,0 255 807 56 14,2 46 5,0 28,7
254 831 60 40,5 (1) 18 26,8 50,1
245 346 60 14,4 75 3,9 44,3
9,7 277 889 64 919 59 3,7 29,3
10,1 253 915 90 24,1 (2) 45 5,4 42,8
13,3 285 185 47 7,8 40 1,22 15,0
Table 3 Thread results polylactide (PLA)
MF (melt flow index) 22 at 210 C and 2.16 kg
In Table 3, the value characterised with (1) emerges from
the otherwise detectable dependencies, also as the greatest
value. In this adjustment, the aerodynamic ratios were
changed by changing the Laval nozzle geometry, likewise
with the value characterised with (2). In the case of (1),
absolutely no splitting of the melt thread took place, at
(2) now and again.
The device according to the invention can be used for
thread-forming melts or solutions but also in general for
liquids if it is a question for example of applying thin
layers, such as colours, paints, finishers. It then serves
for atomising the liquids into as fine as possible droplets
with as uniform as possible a distribution on the surface
to be coated. The conditions can be found easily
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respectively by the given geometric adjustment
possibilities of the device.
The devices (according to Fig. 1, 2 or 3, 4) have in
addition the advantage that a melt or a solution can be
distributed more easily uniformly to individual outflow
openings - here spinning nipples 23 - than if this takes
place from a film, as normally with lines of nozzles. The
nonwoven which is produced is more uniform stripes and in
particular does not have the lines, also termed "lanes", of
a different weight in the direction of travel.
